The use of relatively high molecular weight polyhydroxyl compounds containing fillers for the production of polyurethanes has become increasingly important in recent years. The possibility of improving the properties of polyurethanes by means of organic or inorganic fillers has led to the development of numerous polyhydroxyl compounds containing such fillers dispersed in a finely divided form. The most important representatives of this class of compounds include dispersions of styrene/acrylonitrile copolymers in relatively high molecular weight polyols (German Auslegeschrift 1,152,536; German Patent 1,769,795 and U.S. Pat. Nos. 3,110,695; 3,304,273; 3,383,351; 3,523,093 and 3,637,909); dispersions of polyisocyanate polyaddition products, in particular polyhydrazodicarbonamides (German Auslegeschriften 1,168,075 (British Pat. No. 1,053,131) and 1,260,142 (U.S. Pat. No. 3,325,421); German Offenlegungsschriften 2,512,385 (U.S. Pat. No. 4,246,160); 2,513,815 (U.S. Pat. No. 4,089,835); 2,550,796 (U.S. Pat. No. 4,093,569); 2,550,797 (U.S. Pat. No. 4,147,680); 2,550,833 (U.S. Pat. No. 4,089,835); 2,550,862 (U.S. Pat. No. 4,089,835); 2,633,293 (U.S. Pat. No. 4,093,569); and 2,639,254 (U.S. Pat. Nos. 4,206,109 and 4,260,530)); dispersions of aminoplast resins (German Offenlegungsschriften Nos. 2,324,134 (U.S. Pat. No. 4,225,481); and 2,423,984 (U.S. Pat. No. 4,042,537)); and dispersions of inorganic compounds such as chalk or barium sulphate in polyhydroxyl compounds (German Offenlegungsschriften Nos. 2,654,746 (U.S. Pat. No. 4,207,227); 2,714,291 (U.S. Pat. No. 4,207,227) and 2,739,620 (U.S. Pat. No. 4,198,333 and 4,250,077).
Dispersions containing organic fillers are generally obtained by the direct preparation of the disperse phase in the polyhydroxyl compound. These dispersions are generally stable for considerable periods, but have the disadvantage of stringent production controls. If the dispersions settle due to some external cause, such as the application of excessively high temperatures, it is generally impossible to redisperse them. This phenomenon is an important cause of product rejection in industrial production.
The dispersions of styrene/acrylonitrile copolymers have the added disadvantage that monomer residues present must be removed quantitatively before the dispersions are used. This is due to toxic properties of these monomers. The main disadvantage of inorganic filler dispersions lies in their generally poor stability during storage.
It has now surprisingly been found that very finely divided, sedimentation resistant, reversibly dispersible organic filler dispersions in polyhydroxyl compounds can easily be obtained by solvent-free dispersion of high melting polyesters in low melting, relatively high molecular weight polyhydroxyl compounds. It is surprising that such dispersions can be prepared without the addition of any emulsifiers. This would not be expected by one skilled in the art since sedimentation resistant dispersions of solids cannot generally be prepared without the aid of emulsifiers. When the known process is employed, filler dispersions which are stable in storage are only obtained if emulsifiers are either added to the system at the same time or formed in situ during preparation of the dispersions in the polyhydroxyl compound.